1. Field of the Invention
This invention relates to a method for controlling the tension on a tape web, such as a magnetic tape web, in an apparatus wherein the long tape web is held by engaging-disengaging rolls and processed in various ways, while constant tension is applied to the long tape web. This invention particularly relates to a method for controlling tension with a lock mechanism, wherein the tension applied to a tape web is kept at a predetermined value even during the disengagement of the engaging-disengaging rolls from each other.
2. Description of the Prior Art
In the course of the manufacturing of tapes, such as magnetic tapes, tape webs are moved and various types of processing, such as coating, are carried out on the tape webs. In order to achieve processing uniformly over the overall area of the tape web, the tension applied to the long tape web is adjusted to a predetermined level in each section of an apparatus for manufacturing the tapes. For this purpose, by way of example, a dancer device is used wherein the tension on a tape web is kept at a predetermined value through the vertical movement of a dancer roll. Pairs of engaging-disengaging rolls are located in the tape web movement paths at various sections, such as a calendering section. The engaging-disengaging rolls engage with each other during the ordinary processing of the tape web, and disengage from each other when, for example, a tape web joint passes therebetween. The reason why the engaging-disengaging rolls disengage from each other, i.e. move away from each other, when a tape web joint passes therebetween is that if, for example, the tape web joint is pressed by the engaging-disengaging rolls, an adhesive which is applied at the tape web joint will flow out of the tape web joint or the tape web will be wrinkled However, when the engaging-disengaging rolls disengage from each other in a section of the apparatus in which the tapes are manufactured, the long tape web, which is moving, is released from the holding force of the engaging-disengaging rolls, and therefore the dancer roll of the dancer device moves down or up sharply. Such problems must be eliminated because a dancer device in the next section cannot quickly and accurately control the tension on the tape web.
In order to eliminate the aforesaid problems, subsidiary rolls have heretofore been located in the vicinity of the engaging-disengaging rolls in order to hold a tape web in lieu of the engaging-disengaging rolls while the engaging-disengaging rolls are disengaged from each other. In cases where such subsidiary rolls are provided, the position of the dancer roll does not change sharply even when the engaging-disengaging rolls disengage from each other.
However, in cases where the subsidiary rolls are provided, the apparatus for manufacturing the long tapes becomes large in size and complicated in configuration, and manufacturing the tapes becomes costly.